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Mold Growth on Window Sills: Causes and Prevention

The presence of mold on window sills can cause many problems, including stains and compromised window life span. It can also trigger allergies and other respiratory illnesses. In this blog, local window and door replacement company  Renewal by Andersen® of Southwest Missouri shares a look at the things that you can do to prevent mold growth on window sills.Mold Growth on Window Sills: Causes and Prevention
What Causes Mold Growth on Window Sills?

High moisture levels are conducive to mold growth, which is why it thrives in humid areas such as basements, bathrooms, and attics. Moisture that comes from indoor condensation and humid outside air usually collect at the window sill, and doesn’t immediately dry out.

Exposed wood may also absorb and retain moisture. Sometimes these areas are blocked by window treatments, which would then allow mold to grow undisturbed and hidden from view. Certain types of mold, particularly black mold, are notoriously difficult to remove, even on the best vinyl replacement windows on the market.

The Effects of Mold

We have mentioned how the presence of mold can affect the respiratory system in both children and adults. To elaborate, some people have sensitivity to mold spores, and may develop stuffy nose, coughing, and throat irritation when exposed to high levels mold spores in the air. Skin and eye irritation may accompany these symptoms. Certain types of allergies may also be triggered by mold. A 2004 study conducted by the Institute of Medicine presents evidence that links exposure to mold indoors with asthma, hypersensitivity pneumonitis, and other upper respiratory problems.

How to Prevent Mold Growth on Window Sills

While you can’t completely eliminate mold spores from getting into your home, there are some things that you can do to prevent mold growth on window sills, as well as in other parts of your home:

Maintain Relative Indoor Humidity — Humidity levels change depending on the season: it’s dry during winter and humid during summer. A home humidifier/dehumidifier helps maintain indoor humidity relative to outdoor levels by releasing or absorbing moisture as needed, preventing window condensation and other issues that can lead to mold growth.

Allow Regular Ventilation — Opening your windows for at least 15 minutes a day helps flush out indoor air pollutants, including mold spores. You should also make sure that the air filters in your home ventilation system are replaced when full.

Regularly Clean Your Windows — Make it a point to clean your windows twice a year. Low-maintenance windows with easy cleaning features such as removable or tiltable sashes make this task easier and safer. Make sure that the window treatments are likewise cleaned.

Renewal by Andersen of Southwest Missouri is your leading provider of popular window styles, including double hung replacement windows. Give us a call at (417) 268-9301 or fill out our contact form to schedule an appointment.


"Renewal by Anderson is definitely the way to go for replacement windows. A representative will come out to your house to discuss window replacements, their Fibrex windows, and cost. You do not have to do all the windows at the same time. We chose only to do 10 windows at this time. The price quoted is good for a full year. A few days later another Representative will come out to expertly measure all windows you are choosing to replace. These measurements are sent to the Renewal by Anderson Factory, where your replacement windows are made. Soon after your order has been processed an installation crew shows up with your replacement windows. Renewal by Andersen is excellent in keeping the customer informed from the start of the process to the final installation. We had a crew of 5 that took 2 days for 10 windows. They were definitely top-notch and you could immediately tell they had been installing windows for quite some time. They were definitely prepared for any situation that came up during your window replacement. One window had evidence of past termite infestation. The wood had to be replaced before the installation of our new window. I generally keep an infrared space heater in that room because of all the 5 bay windows. After our new windows were installed, WOW no heat loss. The room no longer felt cooler than the rest of the house. The windows look fantastic. The outside screens are virtually invisible. We love our new windows. You won't be disappointed!!"

Loren Connelly
Nov 17, 2023

"Just had my windows installed. Love them! Wonderful and easy people to work with! Well worth the money! My installers were great! They cleaned up everything and were amazing!"

Sue Waterman
Nov 16, 2023

"Every employee I have met in this company has been very kind and nice to speak with (even when I'm out of town and have to tell them I'm waay out of their zone for promotions lol!) Customizing the front door was fun, and I'm very happy with the end result of a brand new door frame that is sealed well and closes so quietly and smoothly! The frosted glass window panels top to bottom really let in an awesome amount of natural light. The manufacturing process went well with lots of updates along the way, and the salesperson was able to answer every question I had about financing. Can't wait to start upgrading the windows next! As a first time homebuyer I feel very secure in knowing I can call the company and they will make sure their product stays up to their quality standards. They are going to help this 105 year old house stand strong for another 100!"

Kelsey Phelps
Nov 2, 2023

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